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JavaScript RegExp Engine
Regex Tester & Pattern Debugger
Test, validate, and debug regular expressions in real time. Highlights matches visually, inspects captured groups, supports all standard ECMAScript flags, and includes a quick-load pattern library.
Load Pre-built Pattern:
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3 Matches Found
Regular Expressions (RegEx) Quick Reference
A regular expression (regex) is a sequence of characters that specifies a search pattern in text. They are commonly used by strings search algorithms for "find" or "find and replace" operations on strings, or for input validation.
Common Regex Meta-Characters
^ / $: Asserts start / end of string or line
\d / \D: Any digit (0-9) / Any non-digit
\w / \W: Any word character [a-zA-Z0-9_] / Any non-word character
\s / \S: Any whitespace (space, tab, newline) / Non-whitespace
* / + / ?: 0 or more / 1 or more / 0 or 1 occurrence
{n, m}: Between n and m occurrences
Frequently Asked Questions
A standard group (pattern) creates a captured backreference accessible by group index $1, $2. A non-capturing group (?:pattern) matches the subpattern without storing it in memory, saving CPU processing power.
Nested quantifiers like (a+)+ applied to inputs that do not match cause exponential branch checking, freezing the browser. Always anchor expressions and avoid ambiguous nested repetitions.
Privacy Commitment: Zero network transmission. 100% Client-Side browser sandboxed execution.